1. Field of the Invention
The present invention relates to aftermarket engine and transmission interbracing members for HARLEY DAVIDSON type configured motorcycles or the like. In particular, the present invention relates to a structural bracing member which may be attached to the righthand side endplate of a HARLEY DAVIDSON V-twin motor and a righthand side of a transmission, in order to reduce unwanted torquing, pivoting and twisting imparted to the drivetrain through operation of the motorcycle.
2. Background of the Invention
The passion, enthusiasm, and bond that HARLEY DAVIDSON motorcycle owners have for their bikes is well-known. Harley owners and owners of independently manufactured motorcycles and engines based from originally inspired HARLEY DAVIDSON motorcycle designs, continue to modify, customize, and/or improve their “bikes” with various aftermarket parts and accessories.
Furthermore, it is also well-known that Harley owners are very loyal to the traditional V-twin engine layouts that have been the heart and soul of Harleys since the first “Flathead” sold in 1909. However, with the heritage of the V-twin mechanical layout, comes traditional drivetrain deficiencies which have proven disadvantageous and worthy of improvement. One noticeable weak link of a traditional V-twin layout is the arrangement of the engine-to-transmission interface.
In particular, the traditional Harley drivetrain includes a V-twin engine positioned forward the transmission in which both the engine and transmission are independently secured to the motorcycle frame. In one well-known configuration, the drivetrain assembly comprises a leftside drive in which the engine includes a crankshaft and output shaft substantially parallel to an input shaft of the transmission. Engine power is coupled to the transmission with a primary belt and chain interconnecting the parallel output and inputs shafts of the engine and transmission respectively. The drive assembly additionally includes a primary drive housing on the leftside of the motorcycle for enclosing the primary belt or chain interconnecting the parallel output and input shafts.
Over time, the leftside drive has become one of the several characteristic features that motorcycle enthusiasts identify as being representative of tradition and heritage. In this well-known motorcycle drive assembly, the engine and the transmission are typically mounted together by means of generally flat horizontally cantilevered pads that overlap one another at a rear of the engine crankcase and at a front of the transmission case. The two horizontal pads are typically held together by two vertical screws. To maintain proper alignment between the engine and the transmission, the primary housing extends across and bolts to the leftside of both the engine crankcase and the transmission case. The well-known motorcycle configuration also includes a seat post extending from the seat down between the engine and transmission to a cross member joining the tubular members of the lower portion of the frame. Many motorcycle riders and enthusiasts agree that it is desirable to retain the aforementioned features to maintain a classic look.
However, the aforementioned engine-to-transmission interface inherently has its disadvantages. There is minimal direct attachment between the engine and transmission assembly, and the primary drive housing does not provide significant rigidity. For those motorcycles having a horizontal interface between the engine and transmission assembly, there is also a lack of ability to prevent pivoting of the engine about a horizontal and transverse axis with respect to the motorcycle frame.
There have been numerous approaches to solving the aforementioned problem. The entire engine-to-transmission interface has been redesigned as taught in U.S. Pat. Nos. 6,085,855 and 6,241,040 to Schanz et al. and 6,315,072 to Brown et al. However, the contribution of the aforementioned improvement applies only to later model “Evolution” engines and the modern “Twin Cam” engine. Thus, even though a significant advancement for the V-twin engine-to-transmission interface has been made, the aforementioned improvements cannot be economically retrofitted to V-twin engines produced before this significant redesign.
U.S. Pat. No. 5,570,753 to Carlini does teach a motorcycle engine and transmission torque-resisting arm which is designed to overcome the disadvantages for inherent in the traditional V-twin engine-to-transmission interface in which the engine and transmission are separately housed. In this configuration, the engine and transmission cases are coupled on the lefthand side of the primary engine case. A torque resisting arm is provided which is configured to be fitted to the opposite side of the engine and transmission cases from that which the primary engine case occupies is secured to the underlying faces of the engine case and transmission case to provide a torque resisting member there between. The torque resisting arm includes a generally planar engine attachment plate configured to be received upon the engine case and a generally planar spanning plate configured to be received upon the transmission case. The torque resisting arm further defines an offset wall and curved wall extending between the engine attachment plate and the spanning plate.
Although the Carlini torque-resisting arm is certainly an innovative and useful product, it still does have its own disadvantages. For instance, the Carlini arm only secures the three most lower outboard bolts of the engine (See FIG. 1, reference numerals 20, 21, 22) and three lower rightside oriented transmission end bolts (40, 41, 42). Since the Carlini arm is mounted to the engine and transmission in such a limited manner, the overall strengthening effect of the arm is correspondingly limited. Furthermore, the actual strength of the Carlini arm is limited by the moderate to lightweight construction of the arm.
It would be advantageous to provide an interbrace for traditional HARLEY DAVISON V-twin configured motorcycles which experience the unwanted torquing, twisting and pivoting of the drivetrain components. In particular, it would be advantageous to secure the rightsides of both the engine and the transmission with an interbracing member which acts as a supplemental support for maintaining a proper engine-to-transmission interface and to assist in properly securing the engine and transmission into the frame of the motorcycle. Preferably, the interbrace would tie the righthand side of the engine to the righthand side of the transmission. Furthermore, an ideal interbrace would have robustly proportioned mounting portions which act as mounting flanges that are directly secured to the righthand side of the engine and transmission.